External Hard Drive - not recognised

This weekend I solved the following problem:
My external HDD was not recognized by the computer. I am a Windows user.
The drive was not in My computer section, therefore no AutoPlay option, nothing. I checked it in the Device Manager/ Disk Manager and it was there. But no letter was assigned to it. I tried everything. This was successful:
1. First I assigned it a letter with software, called MiniTool Partition Wizard.
2. After that I run the program TestDisk. Here is How To Use It (http://www.techsupportforum.com/forums/f16/have-you-lost-a-hard-drive-partition-or-files-in-your-computer-194492.html)
3. Finally I checked the Disk Manager again, uninstalled the External HDD Device Driver, waited around 15 minutes and plugged it again. (I tried this few times before, but with no visible results).

VOALA! My HDD is working again!